Conventional optical storage devices typically employ a single optical disk having a single recording surface for storing information. Use of a single disk allows the optical components, e.g., a mirror, to be arranged relative to the recording surface in a manner that optimizes the size and cost of the device. Although this results in a low-cost device having a relatively small form factor, its storage capacity is limited to that provided by a single surface. Copending and commonly assigned U.S. patent application of Lee et al., for OPTICAL STORAGE SYSTEM, filed herewith, describes a multiple-surface system in which the beam from a single laser is steered by a stationary galvanometer-rotated mirror to optical heads associated with the respective recording surfaces. The heads are mounted on a carriage that moves them radially over the surfaces for access to selected data tracks on the surfaces.
Specifically, the rotating mirror selectively directs the beam to one of a vertical array of uniquely oriented deflection mirrors. When a deflection mirror receives the beam, it reflects it along a plane parallel to and close to a corresponding disk surface. The beam then passes through an imaging lens on the way to a 45.degree. mirror that redirects the beam radially toward an objective lens in the optical head associated with that surface. The objective lens, in turn, converges the beam on a small spot on the selected data track.
Therefore, it is apparent that the deflection mirrors must be precisely positioned. Moreover, the mirror array must be small to provide compatibility with a form factor for the overall system that is comparable with that of conventional multiple-disk magnetic disk drives. Further, the array must be manufactured within the cost constraints of prior single-disk optical components.
Several fabrication techniques might be employed to produce a deflection mirror array. One approach involves the construction of a precast housing and bonding of the individual mirrors thereto. Each mirror element must be individually handled because of the accuracy required in assembling the mirrors to the housing. This is a substantially difficult and time consuming process because of the small size of the mirrors. The assembly process may further necessitate manual alignment of the mirror array component relative to the remaining optical components of the system. Such individualized construction and alignment procedures are time consuming and costly.
An alternative approach involves plastic molding of the entire array. Although this process provides a low-cost component, current plastic molding technology produces mirror surfaces having a degree of flatness that is insufficient for the intended use of the mirrors. Moreover, because the mirrors are oriented at different angles with respect to the laser beam, each mirror requires a different dielectric coating to reflect the beam. It is difficult and time consuming to provide such coatings in an assembly of mirrors.
Therefore, it is desirable to provide a deflection mirror tower having a plurality of mirrors precisely arrayed along a contoured surface thereof for use in a multiple-disk optical storage device.
It is also desirable to provide a method for mass producing deflection mirror towers, which, if manufactured using existing processes, may be impractical and too costly.
In addition, it is desirable to provide a fabrication process that enables installation of mass produced deflection mirror towers in a storage drive without further adjustment of the mirrors.